Gene for colour blindness in man is located on

The correct option is A X-chromosome only
Colour blindness is a usually a genetic (hereditary) condition (you are born with it). Red/green and blue colour blindness is usually passed down from your parents. The gene which is responsible for the condition is carried on the X chromosome and this is the reason why many more men are affected than women.

So, the correct answer is 'X-chromosome only'.